A related-art vehicle seat includes a seat cushion and a seatback. The seatback has a frame to which a pad is mounted. A lower left part and a lower right part of the frame are respectively connected by reclining apparatuses so that angles thereof with respect to the seat cushion can be adjusted. A connection bar that connects and synchronizes the reclining apparatuses is provided between the reclining apparatuses. The connection bar is provided with a bending mechanism capable of bending the connection bar to suppress the connection bar from being rotated when amounts of deformation at left and right side parts of the seatback, which is caused due to external force applied to the seatback, are different. Accordingly, it is possible to suppress the reclining apparatuses from being unexpectedly released due to the rotation of the connection bar.
However, the bending mechanism has a complicated structure. Accordingly, there are needs for a seatback having a simple structure in which a frame is hardly deformed or rotated by an external force applied to the seatback.